Fabrics obtained by weaving warps and wefts have conventionally been used widely as an industrial fabric. They are, for example, sued in various fields including papermaking wires, conveyor belts and filter cloths and are required to have fabric properties suited for the intended use or using environment. Of such fabrics, a papermaking wire used in a papermaking step for removing water from raw materials by making use of the network of the fabric must satisfy a severe demand. There is therefore a demand for the development of fabrics which do not transfer a wire mark of the fabric and therefore have excellent surface property, have enough rigidity and therefore are usable desirably even under severe environments, or are capable of maintaining conditions necessary for making good paper for a prolonged period of time. In addition, fiber supporting property, improvement in a paper making yield, good water drainage property, wear resistance, dimensional stability and running stability are demanded. In recent years, owing to the speed-up of a paper making machine, requirements for papermaking wires become severe further.
Since most of the demands for industrial fabrics and solutions thereof can be understood if papermaking fabrics on which the most severe demand is imposed among industrial fabrics will be described, the present invention will hereinafter be described by used of the papermaking fabric as a representative example.
Recently, particularly excellent hydration property and surface smoothness have been required due to the high speed operation of a machine for fabric. The Patent Publication 1 discloses a fabric for papermaking which improves hydration property by the fact that the number of upper surface side warps is set to be less than that of lower surface side warps. According to this fabric, longitudinally extending grooves are formed on the upper surface side to improve hydration property, since the number of the upper surface side warps is less. However, said fabric gets easily longitudinally lengthened, since the rigidity in the longitudinal direction of the fabric becomes lowered because of the small number of the upper surface side warps. Thus, said fabric has not been applied to an industrial fabric.
In addition, in the papermaking process, since the upper surface side serves to receive the raw material and serves as a surface contacting wet paper, the fiber supportability and the surface smoothness are required. In this respect, technical problems which cause the fact that the raw material is pulled, or that marks are attached to the paper cannot be solved simply by decreasing the number of the upper surface side warps.    Patent Publication 1: Japanese Patent Laid-open Publication 2005-350844